Acoustic slab



May 12, 1931 M, MAZER I 1,804,884

ACOUSTIC SLAB Filed Sept. 13. 1929 Zmventor Jlhraw Jfazer,

Patented May 12, 1931 PATENT OFFICE MARCUS MAZER, OF PHILADELPHIA,PENNSYLVANIA ACOUSTIC SLAB Application filed September 13, 1929. SerialNo. 382,318.

The present invention relates to the art of acoustics, and has for anobject to provide a building element of stone, stone composition orother suitable hard substance or composition providing a permanentdepressed or indented surface structure incapable of being deformed, thedepressions or indentations having a definite predetermined co-eflicientof absorption.

It is well known that architects, builders and owners often requirestone slabs as a veneer on the inside of their concrete walls. and sincethese stone slabs are very great reflectors of sound, it is an object ofthis 1 invention to provide a slab embodying the above characteristicswhich will enable the architects, buildersor owners to carry out theirdesires of stone slab construction and at the same time to secureperfect acoustic properties in their building.

Another object of the present invention is to provide a slab or the likeadaptable to any desired color or design, with an exposed surface inwhich are formed depressions or indentations to the desired number persquare foot and which may be varied in size so as to give each squarefoot of the slab a predetermined acoustic value. The purpose desired isto enable the manufacture of slabs 3" which may be of the same size butwhich may have greater or lesser absorbing value. Also,

, the purpose is to enable the manufacture of these slabs where theindentations or depressions will present certain designs or configu- 7rations.

Another object of the invention is to provide an acoustic surface whichmay be incorporated in a building unit of any configuration and adaptedfor incorporation in a wall or the like of practically any constructionwhere units are employed, and wherein the units may be of any desiredsize so as to conform with regulation or standard require ments ofslabs, blocks or the like.

47 Various other objects and advantages of this invention will appearfrom the follow ing detailed description of the present shownembodiment, the same being illustrated in the accompanying drawings,wherein 5 Figure 1 is a perspective view of an acoustic slabconstructedaccording to the resent invention and showing a relatively arge numberof indentations or depressions to the square foot to impart a certainpredetermined acoustic value to the slab.

Figure 2 is a-vertical section taken through the same, showing thedepressions in the'exposed surface of the slab.

Figure 3 is a perspective view of a modified form of the acoustic slabwherein a relatively large number of depressions or indentations areformed in the outer or exposed surface of the slab for imparting anacoustic value to the slab differing from that of the slab of Figure 1,and

Figure 4. is a fragmentary enlarged face view of one corner of the.slab, showing a modification in the shape of the depressions orindentations which are formed in the face thereof.

Referring now to the drawings, and first to the form of the inventionshown in Figures 1 and 2, 10 designates the body portion of an acousticslab which may be of suitable dimensions, and which preferably is about1" in thickness. The acoustic slab may be made of any suitable material;one form being a suitable mineral plastic material, precast and dried orbaked with certain depressions or indentations 11 in its outer orexposed face 12 which have a definite predetermined coeflicient ofabsorption. As shown in Figures 1 and 2 these depressions orindentations 11 may be of any desired number and depth within a givensurface area, such as per square foot, and such depth and number of theopenings 11 may be standardized so that the degree of absorption ofthese slabs may be known and they may be installed accordingly.

From Figure 2 it will be noted that the openings 11 are of sufiicientdepth only to provide the necessary air cushioning pockets, the depthbeing varied according to the diameter and number of openings 11 used tomaintain a predetermined co-eflicient of absorption, and from Figure 4it will be noted that the shape of the openings may be varied at willfor the purpose of ornamentation or to otherwise produce differentresults. Another feature of the openings 11 in the face 12 of the slab,is that the openings, indentations or other surface depressions orinterruptions of the slab may vary in shape, width, length, depth ordiameter, according to the general configuration desired, in the sameblock or slab, or the opening 11 in each slab may be all of-the samediameter and depth. The openings 11 may also be arranged as desiredrelatively to one another so as to produce various designs orconfigurations on the face 12 of the slab to properly absorb sound.

' By having the body portion of the slab of adense and rigid material ithas a very low and practically negligible sound absorbing quality and isrigid and permanent as to shape and density. -The provision of theindentations 11 in the face 12 of the slab 10 effects a mechanical meansof absorption which is positive and permanent and which, when onceascertained with a certain number and size of indentations for a givensurface area of slab, may be definitely used to various degrees forobtaining a desired co-efiicient of absorption.

It is a well known fact that co-eflicients of absorption of materialsare at the present time being scientifically ascertained by means ofinstruments made for that purpose.

The co-efiicient of absorption of each slab 10 is determined by thenumber, depth and diameter of the indentations or openings in the face12 of the slab. By changing the number, depth and diameter of theindentations 11 in any given area, the co-eflicient of absorption isnaturally changed.

When, by experiment, it is found that avcertain number of indentationsof a known depth and diameter produce a definite co-efiicient ofabsorption in one slab, for example; percent absorption, other slabswith higher and lower coeflicients of absorption, for example; or 30percent absorption, may be constructed with a proportionately greater orlesser number of the openings of the first slab.

This change in the co-efiicient of absorption may also be effected bychangin the relative depth or diameter or shapes of the indentationswithout changing the number thereof.

When the number of indentations of a given diameter and depth isdetermined for a given surface area of slab, any number of slabs may beconstructed accordingly, and all of theseslabs will have the identicalcoefficient of absorption.

In Figure 3 the modified construction of acoustic slab 13 has in itsouter face 14 a rela- I .tively large number of openings or indentaardslabs may be manufactured and the same may be used as selected in a wallstructure as necessity demands for establishing desired, and correctingany defects, in the acoustic properties of the building.

In the enlarged fragmentary view, Fi ure 4, the openings 16 in the faceof the sla l7 arerelatively lar e and are of polygonal form, and it isunderstood that the openings 16 may be of any desired shape orconfiguration for ornamental or other purposes.

The structure of this fire-proof, non-deformable, hard and unyieldingslab is such that the depressions 11 cannot be altered as to size orshape by pressure on or against the slab, nor by rubbin over the surfaceof the slab; the slab there ore possessing a permanent predetermined anddefinite co-eflicient of absorption I By means of this inventiondefinite and permanent results are obtainable for desirable hearingconditions in a room.

The slabs 10, 13 and 17 may be of any suitable configuration at theirinner or rear sides for securing the slabs to the inner sides ofconcrete walls or the like, and that in other respects the slabs may beof standard materials, shapes or construction.

What is claimed is:

1. An-acoustic slab, comprising a dense, rigid body portion offire-proof material having substantially a minimum inherentco-efficie'nt of scan absorption, said body portion having in itsexposed face a predetermined number of indentations of a depth and sizeproportioned to the absorptive qualit desired, whereby to produce anacoustic sla having a permanent and fixed co-eflicient of absorption andwhich is unalterable in handling and use.

2. An acoustic slab comprisin a tile body portion presenting a sound reecting outer face, and predetermined and permanent means for imparting adesired co-eflicient of absorption to the slab, said means consisting ofa rigid and dense outer face portion on the tile body havingindentations therein selected as to depth, diameter and number to impartthe desired co-efiicient of absorption to the slab.

In testimony whereof I afiix my signature.

. MARCUS MAZER.

